Conventionally, there is known a positioning system using a near distance radio technology. Such a positioning system measures a position of a receiver for receiving a transmitter code based on the transmitter code capable of identifying a transmission transmitted from the transmitter and a radio wave intensity of the transmitted transmitter code. The positioning system executes positioning based on identification information transmitted from a plurality of the transmitters and the radio wave intensities thereof to improve accuracy of the position of the receiver. Further, if the positioning is executed based on the transmitter codes transmitted from the plurality of the transmitters and the radio wave intensities thereof, the positioning system measures the position of the receiver according to a ratio of the radio wave intensities transmitted from the transmitters.
Moreover, the radio wave intensity of the transmitter code transmitted from the transmitter varies due to various factors, and there is a case in which a radio wave intensity stronger than expected is received due to environment in which the transmitter is installed. In such a case, in a conventional positioning system, even if the receiver and the transmitter are present at a substantially the same position, the position of the receiver is measured by containing the transmitter code transmitted from another transmitter and the radio wave intensity thereof. In other words, since the conventional positioning system is strongly influenced by the radio wave intensity in a case in which the radio wave intensity of the transmitter code transmitted from the transmitter that is not located nearby is stronger than expected, the position of the receiver cannot be accurately measured.